1. Technical Field of the Invention
The present invention relates to water-in-water dispersions and more especially, to highly concentrated aqueous dispersions comprising water-soluble polymers and having low viscosity.
2. Description of the Prior Art
Aqueous dispersions of water-soluble polymers are used in various applications and, in particular, as flocculants for the treatment of industrial and municipal waters, the dewatering of sludges, as thickeners and agents for the treatment of soils.
It is known to this art that aqueous water-soluble polymer systems having a high solids content are in the form of a gel and exhibit very high viscosities, which renders them difficult to handle and store. Need exists in this art for such aqueous systems, but which simultaneously have a high solids content and a low viscosity. It is also necessary for such systems to be stable on storage.
U.S. Pat. No. 5,403,883 describes the polymerization, in water, of a mixture of monomers comprising one or more hydrophilic monomers or one or more hydrophobic monomers and, optionally, one or more amphiphilic monomers. The polymerization results in a water-soluble polymer having a high molecular weight. The operation is carried out in the presence of a dispersing polymer incompatible with the water-soluble polymer prepared. The dispersant has a weight-average molecular weight of less than 500,000. A typical dispersant is poly(diallyldimethylammonium chloride), hereinafter denoted as "poly DADMAC."
However, this system of aqueous dispersions exists in the form of a transparent gel having a relatively high viscosity.